
So, why don't we do the same: have everyone, gay or straight, have the exact same "civil union" with the exact same privileges and responsibilities attached? Then, the couple may or may not undergo the religious sacrament at their and their religion's discretion. Let government determine issues like property rights and legal obligations, and religion determine spiritual issues.
Gays would get what they are looking for, which is equality; religions will retain their right to define their own rituals.
But then, a compromise would rob zealots of their chance to froth at the mouth and raise lots of money by fear mongering and demonizing their opposition. So, it probably would never pass.